Yes, I’m having this difficulty too… only tried going to the reworked Uldum. My LATENCY is showing as quite good but input lag is unbearable. The moment I cross back to Silithus, it’s good again (and good in older bfa zones too).
I’ve never actually had this problem previously throughout the expansion.
Anyway, to do what the other people did:
Character: Strakh
Server: Wyrmrest Accord
Location: So far, Uldum. Haven’t tried going to the Vale of Eternal Blossoms yet.
(edit - update, went back around two hours later, things seem to be working properly now… so that’s good!)